Testing Biological Ideas on Evolution, Aging and Longevity with Demographic and Genealogical Data

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Testing Biological Ideas on Evolution, Aging and
Longevity with Demographic and Genealogical Data

• Leonid A. Gavrilov
• Natalia S. Gavrilova
• Center on Aging, NORC/University of Chicago,
• 1155 East 60th Street, Chicago, IL 60637

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What are the data and the predictions of the
evolutionary theory on

• Links between human longevity and fertility
• Lifespan heritability in humans
• Quality of offspring conceived to older parents

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Founding Fathers

• Beeton, M., Yule, G.U., Pearson, K. 1900. Data
  for the problem of evolution in man. V. On the
  correlation between duration of life and the
  number of offspring. Proc. R. Soc. London, 67
  159-179.
• Data used English Quaker records and Whitney
  Family of Connectucut records for females and
  American Whitney family and Burkes Landed
  Gentry for males.

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Findings and Conclusions by Beeton et al., 1900

• They tested predictions of the Darwinian
  evolutionary theory that the fittest individuals
  should leave more offspring.
• Findings Slightly positive relationship between
  postreproductive lifespan (50) of both mothers
  and fathers and the number of offspring.
• Conclusion fertility is correlated with
  longevity even after the fecund period is passed
  and selective mortality reduces the numbers of
  the offspring of the less fit relatively to the
  fitter.

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Other Studies, Which Found Positive Correlation
Between Reproduction and Postreproductive
Longevity

• Telephone inventor Alexander Graham Bell (1918)
• The longer lived parents were the most
  fertile.
• Bettie Freeman (1935) Weak positive correlations
  between the duration of postreproductive life in
  women and the number of offspring borne. Human
  Biology, 7 392-418.
• Bideau A. (1986) Duration of life in women after
  age 45 was longer for those women who borne 12 or
  more children. Population 41 59-72.

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Studies that Found no Relationship Between
Postreproductive Longevity and Reproduction

• Henry L. 1956. Travaux et Documents.
• Gauter, E. and Henry L. 1958. Travaux et
  Documents, 26.
• Knodel, J. 1988. Demographic Behavior in the
  Past.
• Le Bourg et al., 1993. Experimental Gerontology,
  28 217-232.

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Study that Found a Trade-Off Between
Reproductive Success and Postreproductive
Longevity

• Westendorp RGJ, Kirkwood TBL. 1998. Human
  longevity at the cost of reproductive success.
  Nature 396 743-746.
• Extensive media coverage including BBC and over
  100 citations in scientific literature as an
  established scientific fact. Previous studies
  were not quoted and discussed in this article.

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Point estimates of progeny number for married
aristocratic women from different birth cohorts
as a function of age at death. The estimates of
progeny number are adjusted for trends over
calendar time using multiple regression.

• Source Westendorp, Kirkwood, Human longevity at
  the cost of reproductive success. Nature, 1998,
  396, pp 743-746

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Number of progeny and age at first childbirth
dependent on the age at death of married
aristocratic women

• Source Westendorp, R. G. J., Kirkwood, T. B. L.
  Human longevity at the cost of reproductive
  success. Nature, 1998, 396, pp 743-746

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it is not a matter of reduced fertility, but a
case of 'to have or have not'.
Source Toon Ligtenberg Henk Brand. Longevity
does family size matter? Nature, 1998, 396, pp
743-746
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• Source Westendorp, R. G. J., Kirkwood, T. B. L.
  Human longevity at the cost of reproductive
  success. Nature, 1998, 396, pp 743-746

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Do longevous women have impaired fertility ?Why
is this question so important and interesting?
Scientific Significance

• This is a testable prediction of some
  evolutionary theories of aging - disposable soma
  theory of aging (Kirkwood)

"The disposable soma theory on the evolution of
ageing states that longevity requires investments
in somatic maintenance that reduce the resources
available for reproduction (Westendorp,
Kirkwood, Nature, 1998).
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Do longevous women have impaired fertility ?

• Practical Importance.
• Do we really wish to live a long life at the
  cost of infertility?
• the next generations of Homo sapiens will
  have even longer life spans but at the cost of
  impaired fertility
• Rudi Westendorp Are we becoming less
  disposable? EMBO Reports, 2004, 5 2-6.

"... increasing longevity through genetic
manipulation of the mechanisms of aging raises
deep biological and moral questions. These
questions should give us pause before we embark
on the enterprise of extending our lives
Walter Glennon "Extending the Human Life Span",
Journal of Medicine and Philosophy, 2002, Vol.
27, No. 3, pp. 339-354.
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• Educational Significance
• Do we teach our students right?
• Impaired fertility of longevous women is
  often presented in scientific literature and mass
  media as already established fact (Brandt et al.,
  2005 Fessler et al., 2005 Schrempf et al.,
  2005 Tavecchia et al., 2005 Kirkwood, 2002
  Westendorp, 2002, 2004 Glennon, 2002 Perls et
  al., 2002 etc.).
• This "fact" is now included in teaching
  curriculums in biology, ecology and anthropology
  world-wide (USA, UK, Denmark).
• Is it a fact or artifact ?

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General Methodological Principle

• Before making strong conclusions, consider all
  other possible explanations, including potential
  flaws in data quality and analysis
• Previous analysis by Westendorp and Kirkwood was
  made on the assumption of data completenessNumbe
  r of children born Number of children
  recorded
• Potential concerns data incompleteness,
  under-reporting of short-lived children, women
  (because of patrilineal structure of genealogical
  records), persons who did not marry or did not
  have children.Number of children born   gtgt
  Number of children recorded

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Test for Data Completeness

• Direct Test Cross-checking of the initial
  dataset with other data sources
• We examined 335 claims of childlessness in
  the dataset used by Westendorp and Kirkwood.
  When we cross-checked these claims with other
  professional sources of data, we  found that at
  least 107 allegedly childless women (32) did
  have children!
• At least 32 of childlessness claims proved to
  be wrong ("false negative claims") !
• Some illustrative examples
• Henrietta Kerr (16531741) was apparently
  childless in the dataset used by Westendorp and
  Kirkwood and lived 88 years. Our cross-checking
  revealed that she did have at least one child,
  Sir William Scott (2nd Baronet of Thirlstane,
  died on October 8, 1725).
•  Charlotte Primrose (17761864) was also
  considered childless in the initial dataset and
  lived 88 years. Our cross-checking of the data
  revealed that in fact she had as many as five
  children Charlotte (18031886), Henry
  (18061889), Charles (18071882), Arabella
  (1809-1884), and William (18151881).
• Wilhelmina Louise von Anhalt-Bernburg
  (17991882), apparently childless, lived 83
  years. In reality, however, she had at least
  two children, Alexander (18201896) and Georg
  (18261902).

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Point estimates of progeny number for married
aristocratic women from different birth cohorts
as a function of age at death. The estimates of
progeny number are adjusted for trends over
calendar time using multiple regression.

• Source Westendorp, R. G. J., Kirkwood, T. B. L.
  Human longevity at the cost of reproductive
  success. Nature, 1998, 396, pp 743-746

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Antoinette de Bourbon(1493-1583)

• Lived almost 90 years
• She was claimed to have only one child in the
  dataset used by Westendorp and Kirkwood Marie
  (1515-1560), who became a mother of famous Queen
  of Scotland, Mary Stuart.
• Our data cross-checking revealed that in fact
  Antoinette had 12 children!
• Marie 1515-1560
• Francois Ier 1519-1563
• Louise 1521-1542
• Renee 1522-1602
• Charles 1524-1574
• Claude 1526-1573
• Louis 1527-1579
• Philippe 1529-1529
• Pierre 1529
• Antoinette 1531-1561
• Francois 1534-1563
• Rene 1536-1566

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Characteristics of Our Data Sample for
Reproduction-Longevity Studies

• 3,723 married women born in 1500-1875 and
  belonging to the upper European nobility.
• Women with two or more marriages (5) were
  excluded from the analysis in order to facilitate
  the interpretation of results (continuity of
  exposure to childbearing).

• Every case of childlessness has been checked
  using at least two different genealogical
  sources.

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Typical Mistakes in Biological Studies of Human
Longevity

• Using lifespan data for non-extinct birth cohorts
  (cemetery effect)
• Failure to control for birth cohort spurious
  correlations may be found if variables have
  temporal dynamics
• Failure to take into account social events and
  factors e.g., failure to control for age at
  marriage in longevity-reproduction studies

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Childlessness is better outcome than number of
children for testing evolutionary theories of
aging on human data

• Applicable even for population practicing birth
  control (few couple are voluntarily childless)
• Lifespan is not affected by physiological load of
  multiple pregnancies
• Lifespan is not affected by economic hardship
  experienced by large families

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Source Gavrilova et al. Does exceptional human
longevity come with high cost of infertility?
Testing the evolutionary theories of aging.
Annals of the New York Academy of Sciences, 2004,
1019 513-517.
24
Source Gavrilova, Gavrilov. Human longevity and
reproduction An evolutionary perspective. In
Grandmotherhood - The Evolutionary Significance
of the Second Half of Female Life. Rutgers
University Press, 2005 (in press).
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Short Conclusion

• Exceptional human longevity is NOT associated
  with infertility or childlessness

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More Detailed Conclusions

• We have found that previously reported high rate
  of childlessness among long-lived women is an
  artifact of data incompleteness, caused by
  under-reporting of children. After data cleaning,
  cross-checking and supplementation the
  association between exceptional longevity and
  childlessness has disappeared.
• Thus, it is important now to revise a highly
  publicized scientific concept of heavy
  reproductive costs for human longevity. and to
  make corrections in related teaching curriculums
  for students.
• It is also important to disavow the doubts and
  concerns over further extension of human
  lifespan, that were recently cast in biomedical
  ethics because of gullible acceptance of the idea
  of harmful side effects of lifespan extension,
  including infertility (Glannon, 2002).
• There is little doubt that the number of children
  can affect human longevity through complications
  of pregnancies and childbearing, as well as
  through changes in socioeconomic status,  etc. 
  However,  the concept of heavy infertility cost
  of human longevity is not supported by data, when
  these data are carefully reanalyzed.

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Mutation Accumulation Theory of Aging (Medawar,
1946)

• From the evolutionary perspective, aging is an
  inevitable result of the declining force of
  natural selection with age.
• So, over successive generations, late-acting
  deleterious mutations will accumulate, leading to
  an increase in mortality rates late in life.

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Predictions of the Mutation Accumulation Theory
of Aging

• Mutation accumulation theory predicts that those
  deleterious mutations that are expressed in later
  life should have higher frequencies (because
  mutation-selection balance is shifted to higher
  equilibrium frequencies due to smaller selection
  pressure).
• Therefore, expressed genetic variability should
  increase with age (Charlesworth, 1994. Evolution
  in Age-structured Populations).
• This should result in higher heritability
  estimates for lifespan of offspring born to
  longer-lived parents.

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Linearity Principle of Inheritance in
Quantitative Genetics

• Dependence between parental traits and offspring
  traits is linear

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The Best Possible Source on Familial Longevity
Genealogies of European Royal and Noble Families
Marie-Antoinette von Habsburg-Lothringen
(1765-1793)
Charles IX dAnguleme (1550-1574)
Henry VIII Tudor (1491-1547)
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Characteristic of our Dataset

• Over 16,000 persons belonging to the European
  aristocracy
• 1800-1880 extinct birth cohorts
• Adult persons aged 30
• Data extracted from the professional genealogical
  data sources including Genealogisches Handbook
  des Adels, Almanac de Gotha, Burke Peerage and
  Baronetage.

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Daughter's Lifespan(Mean Deviation from Cohort
Life Expectancy)as a Function of Paternal
Lifespan

• Offspring data for adult lifespan (30 years) are
  smoothed by 5-year running average.
• Extinct birth cohorts (born in 1800-1880)
• European aristocratic families. 6,443
  cases

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The Heritability of Life-Spans Is SmallC.E.
Finch, R.E. Tanzi, Science, 1997, p.407
Paradox of low heritability of lifespan vs high
familial clustering of longevity
long life runs in families A. Cournil, T.B.L.
Kirkwood, Trends in Genetics, 2001, p.233
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Heritability Estimates of Human Lifespan
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Is the effect of non-linear inheritance remain
valid after controlling for other explanatory
variables?

• Lifespan of other parent
• Parental ages at childs conception
• Ethnicity
• Month of birth

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Offspring Lifespan at Age 30 as a Function
of Paternal LifespanData are adjusted for
other predictor variables
Daughters, 8,284 cases
Sons, 8,322 cases
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Offspring Lifespan at Age 30 as a Function
of Maternal LifespanData are adjusted for
other predictor variables
Daughters, 8,284 cases
Sons, 8,322 cases
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Is the effect of non-linear inheritance observed
for non-biological relatives?

• We need to test an alternative hypothesis that
  positive effects of long-lived parents on the
  offspring survival may be non-biological and
  caused by common environment and life style
• What about lifespan of spouses?

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Persons Lifespan as a Function of Spouse
LifespanData are adjusted for other predictor
variables
Married Women, 4,530 cases
Married Men, 5,102 cases
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What about lifespan of other relatives?
(sisters vs sisters-in-law)
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Persons Lifespan as a Function of Sisters
LifespanData are adjusted for other predictor
variables
Females, 5,421 cases
Males, 7,378 cases
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Persons Lifespan as a Function of
Sisters-In-Law LifespanData are adjusted for
other predictor variables
Females, 4,789 cases
Males, 4,707 cases
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Mortality Kinetics for Progeny Born to Long-Lived
(80) vs Short-Lived Parents Data are adjusted
for historical changes in lifespan
Sons
Daughters
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Parental-Age Effects in Humans (accumulation of
mutation load in parental germ cells)

• What are the Data and the Predictions of
  Evolutionary Theory on the Quality of Offspring
  Conceived to Older Parents?
• Does progeny conceived to older parents live
  shorter lives?

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Evolutionary Justification for Parental-Age
Effects

• "The evolutionary explanation of senescence
  proposes that selection against alleles with
  deleterious effects manifested only late in life
  is weak because most individuals die earlier for
  extrinsic reasons.
• This argument also applies to alleles whose
  deleterious effects are nongenetically
  transmitted from mother to progeny, that is, that
  affect the performance of progeny produced at
  late ages rather than of the aging individuals
  themselves.
• a decline of offspring quality with parental
  age should receive more attention in the context
  of the evolution of aging.
• Stearns et al. "Decline in offspring
  viability as a manifestation of aging in
  Drosophila melianogaster." Evolution, 2001, Vol.
  55, No. 9, pp. 18221831.

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Genetic Justification for Paternal Age Effects

• Advanced paternal age at child conception is the
  main source of new mutations in human
  populations.
• James F. Crow

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Paternal Age and Risk of Schizophrenia

• Estimated cumulative incidence and percentage of
  offspring estimated to have an onset of
  schizophrenia by age 34 years, for categories of
  paternal age. The numbers above the bars show the
  proportion of offspring who were estimated to
  have an onset of schizophrenia by 34 years of
  age.
• Source Malaspina et al., Arch Gen
  Psychiatry.2001.

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Paternal Age as a Risk Factor for Alzheimer
Disease

• MGAD - major gene for Alzheimer Disease
• Source L. Bertram et al. Neurogenetics, 1998, 1
  277-280.

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Daughters' Lifespan (30) as a Functionof
Paternal Age at Daughter's Birth6,032 daughters
from European aristocratic families born in
1800-1880

• Life expectancy of adult women (30) as a
  function of father's age when these women were
  born (expressed as a difference from the
  reference level for those born to fathers of
  40-44 years).
• The data are point estimates (with standard
  errors) of the differential intercept
  coefficients adjusted for other explanatory
  variables using multiple regression with nominal
  variables.
• Daughters of parents who survived to 50
  years.

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Contour plot for daughters lifespan (deviation
from cohort mean) as a function of paternal
lifespan (X axis) and paternal age at daughters
birth (Y axis)
7984 cases 1800-1880 birth cohorts European
aristocratic families Distance weighted least
squares smooth
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Daughters Lifespan as a Function of
Paternal Age at Daughters Birth Data are
adjusted for other predictor variables
Daughters of shorter-lived fathers (lt80), 6727
cases
Daughters of longer-lived fathers (80), 1349
cases
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Conclusions

• Being conceived to old fathers is a risk factor,
  but it is modulated by paternal longevity
• It is OK to be conceived to old father if he
  lives more than 80 years

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Acknowledgments

• This study was made possible thanks to
• generous support from the National Institute on
  Aging, and
• stimulating working environment at the Center
  on Aging, NORC/University of Chicago

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